Laparoscopic ports facilitate access to the abdominal cavity during endoscopic or minimally invasive surgery. Laparoscopic entry devices require seals to prevent or minimise leakage of insufflation gas through the port when surgical instruments are inserted.
During minimally invasive abdominal surgery, the patient is insufflated with carbon dioxide in order to create space between internal organs and other bodily tissue and thereby create a usable workspace for the surgeon to undertake a given procedure. For this reason a critical feature of any laparoscopic port access system is to ensure that no insufflation gas leaks through the port when instruments of varying sizes are inserted.
During use, the port is first used to puncture the abdominal wall to create an access point through which the surgeon gains access to the abdominal cavity. This puncture is achieved via a component of the port assembly known as the trocar or obturator. The trocar or obturator is then subsequently removed from the assembly leaving the cannula in place, protruding through the abdominal wall of the patient. The patient can then be insufflated, with the cannula remaining in place, to provide the surgeon with an access point to the surgical site—the abdominal cavity. The cannula is the part of the port assembly which contains the seals.
The insufflation gas is prevented from leaking through the cannula due to the presence of a non-return valve within the device. There are several types of non-return valve that can be employed within a cannula body to facilitate this, including flap valves, duckbill valves and quad type valves.
When a surgical instrument is inserted through the port assembly, the non-return valve is forced open. A further seal assembly is therefore required, capable of conforming to the diameter of surgical instruments, to maintain insufflation pressure when the non-return valve is open.
When a surgical instrument is removed from the port assembly, the non-return valve automatically closes, thus preventing leakage of the insufflation gas through the port assembly.
The further seal assembly is a critical aspect a laparoscopic port system. The most basic seal employed to achieve the required functionality is a simple lip seal. This is typically a single piece elastomeric component, consisting of an outside diameter designed to fit inside the cannula housing, and an inside diameter designed to seal around the outside diameter of a surgical instrument. The disadvantage of this form of seal is that it is only designed to seal around one specific diameter of instrument. Therefore, if differing diameter instruments need to be used then more than one port needs to be inserted. To combat this problem, ports using simple lip seals need to incorporate several seals of different diameters which can be manually selected by the user.
One such way this has been achieved is described in GB2441113 which discloses a port system with 3 simple lip seals of different diameters which can be manually selected via pivots on the cannula body. Although a configuration such as this does allow the device to be used with instruments of different diameters, it is undesirable that the user has to manually switch between seals when using multiple instruments of different diameters.
To overcome this requirement for manual seal selection, efforts have been undertaken to develop an improved single or universal seal assembly, capable of automatically conforming to a range of different diameters.
The first universal seal for a port system was described in U.S. Pat. No. 5,395,342 which discloses a seal with a simple conical elastomeric component with a hole at the apex. This elastomeric cone is assembled over a plurality of resilient legs extending inwardly from the inside diameter of the cannula housing.
When an instrument is inserted through the cannula, the distal tip of the instrument firstly makes contact with the resilient legs. The resilient legs are then forced outwards, causing the hole in the apex of the elastomeric cone to dilate to the size of the instrument diameter.
A disadvantage of this solution is the force required to insert a large diameter instrument through the assembly. The user typically desires to feel as little resistance as possible when inserting an instrument through a cannula. This high resistance is due to the fact that a single elastomeric component is being required to expand from below 5 mm diameter to above 12 mm diameter.
Another disadvantage is the high level of friction between the instrument shaft diameter and the seal assembly.
To overcome these problems, seal assemblies comprising a plurality of elastomeric components have been developed.
One such arrangement is set out in US2007185453. In this embodiment, four individual elastomeric leaf components are interwoven at equal angular spacing to form the seal assembly.
This arrangement is advantageous as the overlapping structure requires less force to dilate or expand to accommodate instruments of larger diameters. Another advantage of this design is that under expansion, each individual leaf component is subject to less tension, making the seal less vulnerable to damage from surgical instruments.
A significant disadvantage of this design is that additional components, namely, the individual leaves have to be made. Furthermore, the intricacy of the assembly process adds cost and complexity to the manufacturing process.
Statements of the Invention
According to the present invention, there is provided a surgical access device comprising a seal assembly comprising a plurality of part circular sealing members each attached to a common ring which is held within the device about its longitudinal axis and with the sealing members being located radially inwards of the ring in a stacked relationship, the sealing members being movable, when not within the device, from a position radially outwards of the ring to a position radially inwards of the ring
Accordingly, the sealing assembly of the invention allows an otherwise complex multi-component assembly to be moulded as a single item.
Preferably, the seal assembly comprises a single sheet of flexible material which may be arranged in a single plane with the part circular sealing members in a non-overlapping relationship.
The seal assembly is such that the sealing members extend inwardly in a radial arrangement from an outer integral support ring which, when assembled with corresponding housing components, overlap one another to form a substantially planar surface that has a thickness greater than the individual seal members and has an aperture located at its centre. This facilitates an overlapping formation to be achieved from a single component rather than the intricate assembly of multiple components.
The design of the seal assembly is such that the assembly of the sealing members means that their orientation changes to one another by a predetermined angle about the axis of the cannula such that the orifice is reduced when in an assembled state.
The outermost surfaces of the sealing members become the innermost surface of the component when in their assembled state. This makes the sealing member viable for manufacture via standard injection or compression moulding techniques.
The individual sealing members may be tapered (inclined rather than perpendicular) at their straight edges. This gives an improved airtight seal during use and also reduces friction between the seal member and a surgical instrument shaft.
The individual sealing members are semi-circular in shape. This means that, when assembled, the seal assembly forms a circular footprint when viewed from above. This is preferable for the embodiment of the design into a laparoscopic port system.
The sealing members may include a plurality of orifices adjacent their curved edges to assist in the clamping of the seal in its assembled state. The upper or lower housing may include integral posts to engage in the plurality of orifices.
Preferably, the outer perimeter of the flattened semi-circular seal members are clamped between upper and lower housing components to retain the flattened arrangement during use. This is to ensure that the seal component retains the desired assembled state and does not revert back to its moulded state.
The vertically protruding members may be profiled and dimensioned in such a way that allows them to engage with their mating surface. This is to facilitate a neater arrangement upon assembly.
Preferably, the seal assembly is held within the device by a connection allowing the seal assembly to float relative to the remainder of the device. More preferably, the connection is formed from a flexible elastomeric ring of serpentine configuration.
A flotation device connected to the primary sealing member allows axial movement of small diameter surgical instruments to be absorbed and thereby maintain the airtight seal between the shaft of the surgical instrument and the inner aperture of the sealing member.
The connection may be integral with the seal assembly.
Preferably, the device includes a protective member located adjacent and above (on the proximal side) the primary sealing member, the protective member contacting, in use, said sealing members. The protective member allows the inwardly distal ends of the protective member to contact the innermost diameter of the sealing assembly during use. This is to protect the sealing assembly from potential damage caused by traumatic surgical instruments.
Preferably, the protective member comprises two components, one being located above and rotationally offset from the other. Each component may be in the form of a ring provided with two or more inwardly extending flexible leaves or flaps which allow an instrument to pass through the ring. Preferably, each component is provided with two diametrically opposed flaps.
Preferably, the device is provided with a sealing arrangement axially and distally spaced from said sealing assembly. This sealing arrangement may be a one-way valve such as a duck bill valve. This sealing arrangement provides an airtight seal when no surgical instrument is present.
The present invention further provides a seal core for a surgical access device of the invention, the seal core comprising at least the seal assembly and the protective member as described above.
The present invention also provides a method of assembling a surgical access device having a seal assembly comprising a plurality of part circumferential sealing members each connected to a common support ring, the support ring being held within the device about its longitudinal axis, the sealing members being movable, when not within the device, from a position radially outwards of the ring to a position radially inwards of the ring, the method comprising the step of moving the sealing members from a position radially outwards of the ring to a position radially inwards of the ring, so that said sealing members are in a stacked relationship.